Frictional charging device

ABSTRACT

A frictional charging device ( 30 ) for charging crushed chips ( 1 ) of a plurality of kinds of plastics by stirring them. A stirring vessel ( 31 ) has a friction assisting material ( 52 ) put therein, the particles of the friction assisting material ( 52 ) being so formed that they are larger than the plastic chips ( 1 ). A delivery port ( 34 ) formed in one end of the stirring vessel ( 31 ) is provided with a plurality of delivery area wires ( 47 ) arranged at predetermined intervals and parallel to each other. The spacing between adjacent delivery area wires ( 47 ) is set larger than the plastic chips ( 1 ) and smaller than the particles of the friction assisting material ( 52 ).

TECHNICAL FIELD

The present invention relates to a frictional charging device thatcharges crushed chips of a plurality of kinds of plastics and feeds themto an electrostatic separator used for sorting.

BACKGROUND ART

In recent years, recycling of waste refuse has advanced rapidly. In thisconnection, plastics consumed as raw material for plastic products arethought to be mostly vinyl chloride type resin (hereinafter referred toas PVC), polyethylene type resin (hereinafter referred to as PE), andpolypropylene type resin (hereinafter referred to as PP) and polystyrenetype resin (hereinafter referred to as PS) and it is thought that wasteplastics that are collected are mostly the aforesaid resins. And whenthese resins are to be recycled, it is necessary to sort the resinsaccording to kind.

A method for sorting a mixture of chips of said kinds of plastics willnow be described with reference to FIG. 14.

That is, there is a technique in which first, crushed chips 1 of aplurality of kinds of plastics are charged in a frictional chargingdevice 2. Thereafter, the charged plastic chips 1 are fed from thefrictional charging device 2 to an electrostatic separator 3 used forsorting, where particular plastic chips 1 are separated.

Said frictional charging device 2 is in the form of a cylindrical vessel5 having a loading port 6 formed at one end thereof and a delivery port7 at the other end. Rotatable stirring vanes (not shown) are installedin said cylindrical vessel 5, and a loading hopper 8 is installed atsaid loading port 6.

Further, said electrostatic separator 3 comprises a metal drum electrode10 rotatable around a horizontal axis in a predetermined direction, andan arcuate opposed electrode plate 11 extending in the direction ofrotation of the metal drum electrode 10 and disposed obliquely above andopposed to the latter. The opposed electrode plate 11 has a negativeoutput of a high voltage source 12 connected thereto, while a positiveoutput of the high voltage source 12 is grounded. As a result of thisconnection, a rotary grounded electrode is formed on the metal drumelectrode 10 and a sorting electrostatic field is formed between themetal drum electrode 10 and the opposed electrode plate 11.

Disposed below the metal drum electrode 10 are first and second upwardlyopened separation vessels 13 and 14 arranged in the order mentioned asseen from upstream of the direction of rotation. Further, disposed onthe outer periphery of the metal drum electrode 10 is a brush 15 forscraping off plastic chips 1 sticking to the peripheral surface of themetal drum electrode 10.

The function of the above arrangement will now be described.

The chips 1 of a plurality of kinds of plastics are loaded through theloading hopper 8 into the cylindrical vessel 5, where the chips 1 ofsaid kinds of plastics are stirred to be rubbed against each other bythe stirring vanes rotating therein, whereby they are frictionallycharged. The plastic chips 1 thus charged are delivered from thedelivery port 7 and fall onto the metal drum electrode 10. And thepositively charged plastic chips 1 are repelled by the metal drumelectrode 10 and drawn toward the opposed electrode plate 11 and fallinto the first separation vessel 13. Further, the negatively chargedplastic chips 1 are drawn toward the surface of the metal drum electrode10 and either fall into the second separation vessel 14 with therotation of the metal drum electrode 10 or are scraped off the surfaceof the metal drum electrode 10 by the brush 15 and thereby separated andfall into the second separation vessel 14.

In the aforesaid sorting of plastic chips 1, the following has beenproposed in order to sort out particular plastic chips 1 with higheraccuracy and recover them.

That is, in order that chips 1 of a particular kind of plastic to besorted out and plastic chips 1 having a reverse polarity to that of saidchips 1 of said particular kind of plastic, in the electrification rankfor said kinds of plastics forming the chips 1, may be equal inproportion to each other, particles of either of said plastics should beput as a friction assisting material in the stirring vessel 5.

For example, if said kinds of plastics forming the chips 1 are PVC, PE,PP, PS, these plastics may be arranged in order of electrification rankas PS→PE→PP→PVC. Here, PS is on the positive side of the electrificationrank and PVC is on the negative side of the rank. This shows that PS andPE, when electrified, have a greater amount of positive charge and thatPP and PVC, when electrified, have a greater amount of negative charge.Therefore, in the case where, e.g., PVC is to be sorted out, if theamount of PVC is smaller than the total amount of PS and PE, particlesof PVC are put as a friction assisting material in the cylindricalvessel 5 such that the amount of PVC is equal to the total amount of PSand PE that are on the positive side of the electrification rank andhave a polarity reverse to that of PVC. Further, on the contrary, if theamount of PVC is larger than the total amount of PS and PE, particles ofPS and PE that are on the positive side of the electrification rank andhave a polarity reverse to that of PVC, are put as a friction assistingmaterial in the cylindrical vessel 5. Thereby, PVC is sufficientlyelectrified in a short time to negative polarity, so that PVC can besorted out with high accuracy in the electrostatic separator 3.

However, as described above, in the case where the friction assistingmaterial has been put in the cylindrical vessel 5, the frictionassisting material is also delivered through the delivery port 7 of thecylindrical vessel 5 together with the plastic chips 1, so that there isa problem that a special device is required to recover the deliveredfriction assisting material and put it back again into the cylindricalvessel 5.

As a means for solving the above problem, the following arrangement maybe contemplated. That is, a friction assisting material 18 of largerparticle size than that of plastic chips 1 is used and a net member 16of orthogonal cross pattern is fixedly attached to the delivery portion7 of the cylindrical vessel 5. As shown in FIGS. 15 and 16, the meshes17 of this net member 16 are larger than the plastic chips 1 and smallerthan the friction assisting material 18. The friction assisting material18 is thus confined in the cylindrical vessel 5, whereby the frictionassisting material 18 can be repetitively used.

In the conventional arrangement described above, however, as shown inFIG. 15, even if the meshes 17 of the net member 16 are made larger thanthe plastic chips 1, there occurs a problem that such plastic chips 1are caught by the intersections between the mutually orthogonal wires 16a and 16 b of the net member 16 and gradually clog the meshes 17 of thenet member 16 until troubles occur in delivering the charged plasticchips 1 from the delivery port 7.

Further, as shown in FIG. 16, when plastic chips 1 are about to passthrough the meshes 17 of the net member 16 for delivery from thedelivery port 7, particles of the friction assisting material 18traveling to a point just short of the net member 16 together withplastic chips 1 block up the meshes 17 of the net member 16, presentinga problem that delivery of plastic chips 1 becomes stagnant.

Accordingly, an object of the present invention is provide a frictionalcharging device wherein a friction assisting material is repetitivelyused, whereby particular plastic chips are fully charged in a short timeand the charged plastic chips can be delivered without any trouble.

DISCLOSURE OF THE INVENTION

The present invention provides a frictional charging device that chargescrushed chips of a plurality of kinds of plastics by stirring them andfeeds them to an electrostatic separator used for sorting, saidfrictional charging device being characterized in that said device isprovided with a stirring vessel rotatable around its axis, and a rotarydriving device for rotating said stirring vessel, said stirring vesselhaving a loading port formed at one end thereof for loading plasticchips, said stirring vessel having a delivery port formed at the otherend thereof for delivering charged plastic chips, said delivery portbeing provided with a plurality of delivery area wires arranged alongthe cross-section of the stirring vessel, at predetermined intervals andparallel to each other, wherein in order that chips of a particular kindof plastic to be sorted out and plastic chips having a positive ornegative polarity reverse to that of said chips of said particular kindof plastic, in the electrification rank for said kinds of plasticsforming the chips, may be equal in proportion to each other, particlesof either of said plastics are put as a friction assisting material inthe stirring vessel, the particles of said friction assisting materialbeing so formed that they are larger than the plastic chips, the spacingbetween said delivery area wires being set larger than the plastic chipsand smaller than the particles of the friction assisting material.

According to such arrangement, plastic chips loaded into the stirringvessel through the loading port gradually move within the stirringvessel toward the delivery port and, passing through between thedelivery area wires, they are delivered through the delivery port. Atthis time, since the plastic chips are stirred in the stirring vessel,which is rotating, they are rubbed against each other and against thefriction assisting material and fully frictionally charged in a shorttime.

Further, since the spacing between adjacent delivery area wires is setlarger than the plastic chips and since these delivery area wires arenot of net-like cross construction but are arranged parallel and in thesame direction, the plastic chips reliably pass through between thedelivery area wires without being caught by the delivery area wires andare delivered through the delivery port.

Further, since the spacing between adjacent delivery area wires is setsmaller than the particles of the friction assisting material, theparticles of the friction assisting material cannot pass through betweenthe deliver area wires, so that they remain in the stirring vesselwithout being delivered through the delivery port. Thereby, the frictionassisting material can be repetitively used.

Further, the invention provides a frictional charging devicecharacterized in that disposed intermediate between the loading port andthe delivery port are a plurality of intermediate wires arranged alongthe cross-section of the stirring vessel, at predetermined intervals andparallel to each other, the spacing between said intermediate wiresbeing set larger than the plastic chips and smaller than the particlesof the friction assisting material, the delivery area wires and theintermediate wires differing from each other in direction peripherallyof the stirring vessel.

According to such arrangement, the plastic chips loaded into thestirring vessel, which is rotating, through the loading port graduallymove within the stirring vessel toward the delivery port, passingthrough between the intermediate wires and then through between thedelivery area wires, whereupon they are delivered through the deliveryport.

Further, the invention provides a frictional charging devicecharacterized in that the stirring vessel is inclined such that thedelivery port side is positioned below the level of the loading portside.

According to such arrangement, the plastic chips loaded into thestirring vessel through the loading port gradually move toward thedelivery port owing to the inclination of the stirring vessel, untilthey are reliably delivered through the delivery port with almost noplastic chips remaining in the stirring vessel.

Further, the invention provides a frictional charging devicecharacterized by including a delivery area adjuster for adjusting thearea of an opening in the delivery port.

According to such arrangement, the delivery rate of the plastic chipscan be adjusted by increasing or decreasing the area of the opening inthe delivery port by the delivery area adjuster.

Further, the invention provides a frictional charging devicecharacterized by including a stirring member disposed in the stirringvessel for stirring the plastic chips.

According to such arrangement, the plastic chips loaded into thestirring vessel are fully stirred by the rotation of the stirring vesseland by the stirring member, during which stirring, the plastic chips arereliably rubbed against each other and against the friction assistingmaterial.

Further, the invention provides a frictional charging device thatcharges crushed chips of a plurality of kinds of plastics by stirringthem and feeds them to an electrostatic separator used for sorting, saidfrictional charging device being characterized in that an inner sleevehaving a number of openings extending therethrough is rotatablyinstalled inside an outer sleeve, said outer sleeve being provided witha loading port for loading plastic chips into the outer sleeve, and adelivery port for delivering the plastic chips, delivered from theinside of the inner sleeve, to the outside of the outer sleeve, whereinin order that chips of a particular kind of plastic to be sorted out andplastic chips having a reverse polarity to said chips of said particularkind of plastic, in the electrification rank for a plurality of kinds ofplastics forming the chips, may be equal in proportion to each other,particles of either of said plastics are put as a friction assistingmaterial in the inner sleeve, the particles of said friction assistingmaterial being so formed that they are larger than the plastic chips,the openings in said inner sleeve being formed to be larger than theplastic chips and smaller than the particles of the friction assistingmaterial.

According to such arrangement, the plastic chips loaded into the outersleeve through the loading portion enter the inner sleeve, which isrotating, through the openings in the inner sleeve to be stirredtherein. Therefore, the plastic chips are rubbed against each other andagainst the friction assisting material, so that they are fullyfrictionally charged in a short time.

The plastic chips thus charged move out of the inner sleeve through theopenings to the outside of the inner sleeve, whereupon they aredelivered through the delivery portion to the outside of the outersleeve. Further, since the friction assisting material cannot passthrough the openings in the inner sleeve, they remain in the innersleeve. Thereby, the friction assisting material can be repetitivelyused.

The rotation of the inner sleeve causes the friction assisting materialto roll on the inner peripheral surface of the inner sleeve, therebypreventing the friction assisting material clogging the openings in theinner sleeve. Therefore, the plastic chips reliably pass through theopenings in the inner sleeve to be delivered out of the inner sleeve tothe outside of the latter.

Further, the invention provides a frictional charging devicecharacterized in that the inner sleeve is rotatable around a horizontalaxis, the loading portion is formed in the upper region of the outersleeve, while the delivery portion is formed in the lower region of theouter sleeve, and said inner sleeve is located at a vertical positionbetween the loading portion and the delivery portion.

According to such arrangement, the plastic chips loaded into the outersleeve through the loading portion, while falling, enters the innersleeve, which is rotating, through the openings in the inner sleeve.Further, the plastic chips delivered to the outside of the inner sleevethrough the openings in the inner sleeve, while falling, are deliveredto the outside of the outer sleeve through the delivery portion. Thus,the utilization of the falling of the plastic chips in loading anddelivering them ensures smooth loading and delivery of the plasticchips.

Further, the invention provides a frictional charging devicecharacterized in that the inner sleeve is composed of an inner sleevemain body shaped like a sleeve, and end members for closing the oppositeends of said inner sleeve main body, and said inner sleeve main body andsaid end members are respectively formed with a number of openings.

According to such arrangement, since a number of openings are formed inthe entire surface of the inner sleeve, the loading and delivery of theplastic chips are effected through the entire surface of the innersleeve. Therefore, even if clogging of some openings should locallyoccur in the inner sleeve, the plastic chips pass through the otheropenings, so that almost no trouble occurs.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a longitudinal section of the stirring vessel of a frictionalcharging device according to an embodiment 1 of the present invention;

FIG. 2 is a view showing said frictional charging device and anelectrostatic separator disposed downstream of said frictional chargingdevice;

FIG. 3 is a view taken along the line A—A in FIG. 1;

FIG. 4 is a view taken along the line B—B in FIG. 1;

FIG. 5 is an enlarged view of the delivery area adjuster of saidfrictional charging device;

FIG. 6 is a view taken along the line C—C in FIG. 1;

FIG. 7 is a view taken along the line D—D in FIG. 1;

FIG. 8 is a front view, in section, of a frictional charging deviceaccording to an embodiment 2 of the invention;

FIG. 9 is a perspective view, partly broken away, of said frictionalcharging device;

FIG. 10 is a side view, in section, of said frictional charging device;

FIG. 11 is an enlarged view of a net member in the inner sleeve of saidfrictional charging device;

FIG. 12 is a schematic view showing said frictional charging device andelectrostatic separator;

FIG. 13 is an enlarged view of the slits in the inner sleeve of africtional charging device according to an embodiment 3 of theinvention;

FIG. 14 is a schematic view showing a conventional frictional chargingdevice and a conventional electrostatic separator;

FIG. 15 is an enlarged front view of a net member installed in thedelivery port of said conventional frictional charging device; and

FIG. 16 is a view taken along the line A—A in FIG. 15.

BEST MODE FOR EMBODYING THE INVENTION

To give a detailed description of the invention, first, an embodiment 1of the invention will be described with reference to FIGS. 1 through 7.In addition, since an electrostatic separator 3 has the same arrangementas the conventional one described above, like reference numerals areadded to omit a description thereof.

As shown in FIGS. 1 and 2, the numeral 30 denotes a frictional chargingdevice for charging crushed plastic chips 1 by stirring them. Thisfrictional charging device 30 comprises a cylindrical stirring vessel31, and a loading hopper 32 for loading crushed plastic chips 1 intosaid stirring vessel 31.

One end of said stirring vessel 31 is formed with a loading port 33.Said loading port 33 has the lower portion of said loading hopper 32connected thereto through a bearing 53. Further, the other end of thestirring vessel 31 is formed with a delivery port 34 for delivery ofcharged plastic chips 1. The plastic chips 1 delivered from saiddelivery port 34 slide inside and down a feed tray 35 and are fed onto ametal drum electrode 10 of the electrostatic separator 3.

Said stirring vessel 31 is turnably attached to a support frame 49through bearings or the like (not shown) and is rotated around an axis39 by a rotary driving device 38 composed of a motor 36 and a drivingbelt 37. Further, said support frame 49 is arranged for vertical turningmotion around one end thereof and is turned as by a cylinder device (notshown). Thus, turning the support frame 49 changes the inclination angleα of the stirring vessel 31. At this time, the stirring vessel 31 istilted such that its delivery port 34 is positioned below the level ofits loading port 33.

Further, as shown in FIGS. 1 and 3, the inner peripheral surface of saidstirring vessel 31 is provided with a plurality of stirring vanes 40 (anexample of a stirring member) peripherally disposed at predeterminedangular intervals and extending from the loading port 33 to the deliveryport 34.

Further, the stirring vessel 31 is internally provided with a supportshaft 41 extending along an axis 39. One end of said support shaft 41 isattached to the lower end of the loading hopper 32. Said support shaft41 is provided with a plurality of stirring rods 42 a, 42 b (an exampleof a stirring member) extending radially outward from the axis 39 of thestirring vessel 31. In addition, one plurality of stirring rods 42 a arepositioned on the side of the loading port 33 in the stirring vessel 31.And the other plurality of stirring rods 42 b are positioned closer tothe delivery port 34 in the stirring vessel 31. Further, the stirringvessel 31 is a vessel that is made of metal or whose inner peripheralsurface is coated with resin.

Further, as shown in FIGS. 1 and 5, the delivery port 34 is providedwith a delivery area adjuster 43 for adjusting the area of the openingin the delivery port 34. That is, the delivery area adjuster 43 iscomposed of a semicircular fixed plate 44 covering substantially halfthe delivery port 34, and a semicircular movable plate 45 turnablearound the axis 39 to overlap said fixed plate 44. The movable plate 45is fitted on the other end of the support shaft 41 and is therebysupported.

Further, as shown in FIGS. 1 and 6, the delivery port 34 is providedwith a plurality of delivery area wires 47 arranged along thecross-section of the stirring vessel 31 orthogonal to its axis 39, atpredetermined intervals of S₁ and parallel to each other. These deliveryarea wires 47 are positioned inside the delivery area adjuster 43. Thedelivery area wires 47 are fixedly attached at their opposite ends tothe inner peripheral surface of the stirring vessel 31.

Similarly, as shown in FIGS. 1 and 7, disposed intermediate between theloading port 33 and the delivery port 34 are a plurality of intermediatewires 48 arranged along the cross-section of the stirring vessel 31orthogonal to its axis 39, at predetermined intervals of S₁ and parallelto each other. These intermediate wires 48 are fixedly attached at theiropposite ends to the inner peripheral surface of the stirring vessel 31.And as shown in FIGS. 6 and 7, the respective directions of the deliveryarea wires 47 and intermediate wires 48 are shifted by 90° peripherallyof the stirring vessel 31. As shown in FIG. 1, the stirring vessel 31 isinternally divided at the intermediate wires 48 into a first stirringchamber 50 positioned on the side of the loading port 33 and a secondstirring chamber 51 positioned on the side of the delivery port 34. Inaddition, said one plurality of stirring rods 42 a are positioned in thefirst stirring chamber 50 and the other plurality of stirring rods 42 bare positioned in the second stirring chamber 51.

Further, as shown in FIG. 1, in order that chips 1 of a particular kindof plastic to be sorted out and plastic chips 1 having a positive ornegative polarity reverse to that of said chips 1 of said particularkind of plastic, in the electrification rank for said kinds of plasticsforming the chips 1, may be equal in proportion to each other, particlesof either of said plastics are put as a friction assisting material 52in the stirring vessel 31. The particles of said friction assistingmaterial 52 are larger than the chips 1 of said kinds of plastics. Asshown in FIGS. 6 and 7, the spacing S₁ in each of said wires 47 and 48is set larger than the plastic chips 1 and smaller than the particles ofthe friction assisting material 52.

For example, in the case of a mixture of chips 1 of said kinds ofplastics such as PVC, PE, PP, PS, these plastics, when arranged in orderof electrification rank, may be arranged in order of electrificationrank as PS→PE→PP→PVC. Here, PS is on the positive side of theelectrification rank and PVC is on the negative side of the rank. In thecase where, e.g., PVC is to be sorted out, if the amount of PVC issmaller than the total amount of PS and PE, particles of PVC are put asa friction assisting material in the stirring vessel 31 such that theamount of PVC is equal to the total amount of PS and PE that have areverse polarity to that of PVC. On the contrary, if the amount of PVCis larger than the total amount of PS and PE, particles of PS and PEthat are on the positive side of the electrification rank and have areverse polarity to that of PVC, are put as a friction assistingmaterial 52 in the stirring vessel 31. Thus, since the amount of PVC ismade equal to the total amount of PS and PE having a reverse polarity tothat of PVC, PVC is sufficiently electrified in a short time to negativepolarity, so that PVC can be sorted out with high accuracy in theelectrostatic separator 3.

The friction assisting material 52 selected in the manner describedabove is put in the first and second stirring chambers 50 and 51 in thestirring vessel 31 and while the stirring vessel 31 is being rotated bythe rotary driving device 38, crushed plastic chips 1 are loaded intothe stirring vessel 31 through the loading hopper 32.

Thereby, the plastic chips 1 loaded into the first stirring chamber 50through the loading port 33 gradually move within the inclined stirringvessel 31 toward the delivery port 34, passing through between theintermediate wires 48 into the second stirring chamber 51, then passingthrough between the delivery area wires 47, whereupon they are deliveredthrough the delivery port 34. At this time, the plastic chips 1 in thestirring vessel 31 are reliably stirred by the stirring vanes 40rotating with the stirring vessel 31 and by the stirring rods 42 a and42 b stationary relative to the stirring vessel 31. Therefore, theplastic chips 1 are rubbed against each other and against the frictionassisting material 52, so that they are fully frictionally charged in ashort time.

In addition, as shown in FIG. 6, since the spacing S₁ between adjacentdelivery area wires 47 is set larger than the plastic chips 1 and sincethese delivery area wires 47 are not of net-like cross construction butare arranged parallel and in the same direction, the plastic chips 1reliably pass through between the delivery area wires 47 without beingcaught by the delivery area wires 47 and are delivered through thedelivery port 34.

Further, since the spacing S₁ between adjacent delivery area wires 47 isset smaller than the particles of the friction assisting material 52,the particles of the friction assisting material 52 cannot pass throughbetween the deliver area wires 47, so that they remain in the stirringvessel 31 without being delivered through the delivery port 34. Thereby,the friction assisting material 52 can be repetitively used.

In addition, as shown in FIG. 7, it is also possible for theintermediate wires 48 to provide the same function and effect as thoseprovided by the delivery area wires 47.

Further, as shown in FIG. 5, since the area of the opening in thedelivery port 34 can be increased or decreased by turning the movableplate 45 in the direction of arrow W, the delivery rate of the plasticchips 1 being delivered through the delivery port 34 can be adjusted.Further, the delivery rate of said plastic chips 1 can also be adjustedby the rpm of the stirring vessel 31, the angle of inclination α, or thewire diameter or the spacing S₁ of the wires 47, 48.

The plastic chips 1 thus delivered through the delivery port 34, fullycharged, are fed as shown in FIG. 2 through the feed tray 35 onto themetal drum electrode 10 and sorted into two groups, one fed into thefirst separation vessels 13 and the other into the second separationvessel 14, according to kind.

In said embodiment 1, in the case of sorting, for example, PVC from thechips 1 of said kinds of plastics such as PVC, PE, PP and PS, particlesof PVC or particles of PS and PE that are on the positive side of theelectrification rank are used as the friction assisting material 52according to the PVC content. However, the same effect may also beobtained by using particles of PP that is located intermediate in theelectrification rank, as a friction assisting material 52. Further,particles of a metal such as stainless steel, may be used as thefriction assisting material 52.

Further, as shown in FIG. 1, the other end of the stirring vessel 31 isprovided with a flange 54, and the flange 54 is formed with a pluralityof bolt holes 55 and is bolted to the flange 54 of another stirringvessel 31 shown in phantom lines; in this manner, two stirring vessels31 can be joined together. This makes possible the frictional chargingof a large amount of plastic chips 1. In this case, however, thedelivery area adjuster 43 will be provided only in this separate, newlyconnected stirring vessel 31 shown in phantom lines and the deliveryarea adjuster 43 of the stirring vessel 31 shown in solid lines will beremoved.

Further, in said embodiment 1, with the stirring vessel 31 inclined asshown in solid lines in FIG. 2, plastic chips 1 are loaded into thestirring vessel 31 for friction charging; however, with the stirringvessel 31 held horizontal, plastic chips 1 may be loaded into thestirring vessel 31 for frictional charging and after the lapse of apredetermined time when the plastic chips 1 have been fully frictionallycharged, the stirring vessel 31 may be tilted to deliver the plasticchips 1 through the delivery port 34.

Further, in said embodiment 1, as shown in FIGS. 6 and 7, the respectivedirections of the delivery area wires 47 and intermediate wires 48 areshifted by 90° peripherally of the stirring vessel 31; however, they maybe shifted by other angle than 90° or instead of shifting, said wires 47and 48 may be arranged in the same direction.

An embodiment 2 of the invention will now be described with reference toFIGS. 8 through 12 of the accompanying drawings. In addition, since theelectrostatic separator 3 is the same arrangement as the conventionalone described above, like reference numerals are added to omit adescription thereof.

As shown in FIGS. 8 through 10, the numeral 70 denotes a frictionalcharging device for charging a mixture of crushed chips 1 of a pluralityof kinds of plastics by stirring them. This frictional charging device70 comprises an outer sleeve 71 and an inner sleeve 72. The outer sleeve71 is composed of an outer sleeve drum 73 U-shaped in a front view, aroof plate 74 disposed on top of the outer sleeve drum 73, and endplates 75 disposed on the front and rear ends of the outer sleeve drum73 and is thus made hollow.

The roof plate 74 is formed with a loading port 77 (an example of aloading portion) for loading plastic chips 1 into the outer sleeve 71.The lower end of a loading hopper 78 is connected to this loading port77.

Further, the lower portion of said outer sleeve drum 73 is formed with adelivery port 79 (an example of a delivery portion) for delivering theplastic chips 1, delivered from the inner sleeve 72, to the outside ofthe outer sleeve 71. The plastic chips 1 delivered through the deliveryport 79, as shown in FIG. 12, slide inside and down a feed tray 95 andare fed onto a metal drum electrode 10 of the electrostatic separator 3.The delivery port 79 is in elongated form, extending from the front endto the rear end of the outer sleeve drum 73 and is opened and closed byan opening/closing plate 80 turnably installed in the outer sleeve drum73. In addition, the opening and closing operation of theopening/closing plate 80 is effected by a cylinder device (not shown).

The inner sleeve 72 is installed within the outer sleeve 71 for rotationaround a horizontal axis 82 and is located at a vertical positionbetween the loading port 77 and the delivery port 79. Further, the innersleeve 72 comprises the inner sleeve main body 83 in the form of anoctagonal sleeve, and end members 84 disposed on the front and rear endsof said inner sleeve main body 83. Further, the inner sleeve main body83 comprises a plurality of frames 93 disposed in a direction along thehorizontal axis 82, and net members 97 attached between these frames 93.Further, each of said end members 84 comprises a plurality of frames 94radially extending from the horizontal axis 82, and a net member 97attached to said frame members 94.

The net members 97 have a number of meshes 91 (an example of an opening)extending through the inner and outer sides of the inner sleeve 72.Further, the end members 84 on the front and rear sides are centrallyprovided with rotary shafts 85. These rotary shafts 85 are rotatablysupported in the end plates 75 on the front and rear sides of the outersleeve 71 through bearings 96. The front end of either of these frontand rear rotary shafts 85 extends through said end plate 75 to theoutside and is connected to a rotary driving device 86. The rotarydriving device 86 comprises a motor 87 mounted outside the outer sleeve71, pulleys 88 and 89, and a driving belt 90.

Further, the outer peripheral surface of the inner sleeve 72 is providedwith a plurality of plate-like vane members 98 for scraping off plasticchips 1 collected between the outer and inner sleeves 71 and 72. Thesevane members 98 have a length that is substantially equal to the lengthof the inner sleeve 72 in the direction of the horizontal axis 82 andare four in all, attached to every second one of the eight apexes of theinner sleeve 72.

Further, as shown in FIG. 8, in order that chips 1 of a particular kindof plastic to be sorted out and plastic chips 1 having a reversepolarity to said chips 1 of said particular kind of plastic, in theelectrification rank for a plurality of kinds of plastics forming thechips 1, may be equal in proportion to each other, particles of eitherof said plastics are put as a friction assisting material 92 in theinner sleeve 72. In addition, the particles of said friction assistingmaterial 92 are so formed that they are larger than the chips 1 of saidkinds of plastics. Further, as shown in FIG. 11, the spacing S₂ in eachof the meshes 91 in the net members 97 of the inner sleeve 72 is setlarger than the plastic chips 1 and smaller than the particles of thefriction assisting material 92.

For example, in the case of a mixture of chips 1 of said kinds ofplastics such as PVC, PE, PP, PS, these plastics may be arranged inorder of electrification rank as PS→PE→PP→PVC. Here, PS is on thepositive side of the electrification rank and PVC is on the negativeside of the rank. In the case where, e.g., PVC is to be sorted out, ifthe amount of PVC is smaller than the total amount of PS and PE,particles of PVC are put as a friction assisting material 92 in theinner sleeve 72 such that the amount of PVC is equal to the total amountof PS and PE that are on the positive side of the electrification rankand have a reverse polarity to that of PVC. Further, on the contrary, ifthe amount of PVC is larger than the total amount of PS and PE,particles of PS and PE that have a reverse polarity to that of PVC, areput as a friction assisting material 92 in the inner sleeve 72. Thereby,the amount of PVC becomes equal to the total amount of PS and PE havinga reverse polarity to that of PVC, so that PVC is sufficientlyelectrified in a short time to negative polarity, and hence PVC can besorted out with high accuracy in the electrostatic separator 3.

The friction assisting material 92 selected in the manner describedabove is put in the inner sleeve 72 and while the inner sleeve 72 isbeing rotated by the rotary driving device 86, crushed plastic chips 1are loaded into the loading hopper 78. In addition, at this time, thedelivery port 79 has been closed by the opening/closing plate 80.

The plastic chips 1 loaded into the loading hopper 78, while falling,pass through the meshes 91 of the rotating inner sleeve 72 into theinner sleeve 72, where they are stirred. Thereby, the plastic chips 1are rubbed against each other and against the friction assistingmaterial 92, so that they are fully frictionally charged in a shorttime.

In addition, in the case where some of the plastic chips 1 loaded intothe loading hopper 78 spill down the outer peripheral surface of theinner sleeve 72 to collect between the outer and inner sleeves 71 and72, the plastic chips 1 spilled outside the inner sleeve 72 are scrapedupward by the vane members 98 rotating integrally with the inner sleeve72, thereby reliably passing through the meshes 91 to enter the innersleeve 72. Further, the plastic chips 1 moving out of the inner sleeve72 through the meshes 91 to the outside of the inner sleeve 72 are alsorepetitively scraped upward by the vane members 98, so that they againpass through the meshes 91 to enter the inner sleeve 72.

After the plastic chips 1 have thus been electrified for a given time,the opening/closing plate 80 is turned to open the delivery port 79.Thereby, the electrified plastic chips 1 are delivered from the innersleeve 72 through the meshes 91 to the outside of the inner sleeve 72and then to the outside of the outer sleeve 71 through the delivery port79 while falling. At this time, the plastic chips 1 collected betweenthe outer and inner sleeves 71 and 72 are pushed by the vane members 98rotating integrally with the inner sleeve 72 and forcibly delivered fromthe delivery port 79. Therefore, the plastic chips 1 can be reliablydelivered from the inner sleeve 71.

Further, since the friction assisting material 92 cannot pass throughthe meshes 91 of the net members 97 of the inner sleeve 72, it remainsin the inner sleeve 72. Thereby, the friction assisting material 92 canbe repetitively used.

Further, since the friction assisting material 92 rolls on the innerperipheral surface of the inner sleeve 72 owing to the rotation of theinner sleeve 72, it is possible to prevent the friction assistingmaterial 92 from blocking the meshes 91 of the net members 97 of theinner sleeve 72. Therefore, the plastic chips 1 reliably pass throughthe meshes 91 of the inner sleeve 72 to be delivered from the innersleeve 72 to the outside of the latter.

The plastic chips 1 thus delivered through the delivery port 79, fullycharged, are fed as shown in FIG. 12 through the feed tray 95 onto themetal drum electrode 10 and sorted into two groups, one fed into thefirst separation vessels 13 and the other into the second separationvessel 14, according to kind.

In said embodiment 2, as shown in FIG. 9, since the many meshes 91 areformed in the entire surface (outer peripheral surface and opposite endsurfaces) of the inner sleeve 72, the loading and delivery of theplastic chips 1 are effected through the entire surface of the innersleeve 72. Therefore, even if clogging of some meshes 91 should locallyoccur in the inner sleeve 72, the plastic chips 1 pass through the othermeshes 91, so that almost no trouble occurs.

In said embodiment 2, as shown in FIG. 8, the inner sleeve 72 ispositioned between the upper loading port 77 and the lower delivery port79, utilizing the falling of the plastic chips 1 for loading anddelivering the plastic chips 1; therefore, the loading and delivering ofthe plastic chips 1 can be smoothly effected.

In said embodiment 2, when the inner sleeve 72 is rotating to stir theplastic chips 1, the delivery port 79 is kept closed by theopening/closing plate 80 for the time required for sufficient stirring.This prevents the situation in which the plastic chips 1 are deliveredthough the delivery port 79 in the state of not being sufficientlyelectrified.

In said embodiment 2, in the case of sorting, for example, PVC from thechips 1 of a plurality of kinds of plastics such as PVC, PE, PP and PS,particles of PVC or particles of PS and PE that are on the positive sideof the electrification rank are used as the friction assisting material92 according to the PVC content. However, the same effect may also beobtained by using particles of PP that is located intermediate in theelectrification rank, as a friction assisting material 92. Further,particles of a metal such as stainless steel, may be used as thefriction assisting material 92.

In said embodiment 2, the plastic chips 1 in the inner sleeve 72 can bethoroughly stirred by rotating the inner sleeve 72. Further, the innersleeve 72 may be internally provided with bar-like or vane-like stirringmembers to ensure more reliable stirring.

In said embodiment 2, as shown in FIG. 8, the inner sleeve main body 83of the inner sleeve 72 is in the form of an octagonal sleeve; however,it may be a polygonal, other than octagonal, sleeve or a circularsleeve.

In said embodiment 2, as shown in FIG. 8, four vane members 98 areattached to the inner sleeve 72, but the number is not limited to four,and a single or a plurality of, other than four, vane members may beattached thereto. For example, eight vane members 98 may each beattached to one of the eight apexes of the inner sleeve 72.

In said embodiment 2, as shown in FIG. 9, the position at which theloading port 77 and loading hopper 78 are attached may be a longitudinalend or intermediate position on the roof plate 74 of the outer sleeve71. Further, as in the case of the delivery port 79, the loading port 77and loading hopper 78 may be in elongated form, extending from the frontend to the rear end of the roof plate 74.

In said embodiment 2, as an example of an opening formed in the innersleeve 72, there is cited, as shown in FIG. 11, meshes 91 in the netmembers 97 formed of wires in an orthogonal cross pattern. In contrastthereto, as an embodiment 3, as shown in FIG. 13 a number of wires orbars may be arranged to extend in one direction at predeterminedintervals and parallel to each other to form a number of slits 99 (anexample of an opening). In this case, the spacing S₃ between these slits99 is set larger than the plastic chips 1 and smaller than the particlesof the friction assisting material 92.

INDUSTRIAL APPLICABILITY

As described above, the frictional charging device according to theinvention is suitable for repetitively using a friction assistingmaterial when chips of a plurality of kinds of plastics are to bestirred for electrification.

What is claimed is:
 1. A frictional charging device that charges crushedchips of a plurality of kinds of plastics by stirring them and feedsthem to an electrostatic separator used for sorting, said frictionalcharging device being characterized in that said device is provided witha stirring vessel rotatable around its axis, and a rotary driving devicefor rotating said stirring vessel, said stirring vessel having a loadingport formed at one end thereof for loading plastic chips, said stirringvessel having a delivery port formed at the other end thereof fordelivering charged plastic chips, said delivery port being provided witha plurality of delivery area wires arranged along the cross-section ofthe stirring vessel, at predetermined intervals and parallel to eachother, wherein in order that chips of a particular kind of plastic to besorted out and plastic chips having a positive or negative polarityreverse to that of said chips of said particular kind of plastic, in theelectrification rank for said kinds of plastics forming the chips, maybe equal in proportion to each other, particles of either of saidplastics are put as a friction assisting material in the stirringvessel, the particles of said friction assisting material being soformed that they are larger than the plastic chips, the spacing betweensaid delivery area wires being set larger than the plastic chips andsmaller than the particles of the friction assisting material.
 2. Africtional charging device as set forth in claim 1, characterized inthat disposed intermediate between the loading port and the deliveryport are a plurality of intermediate wires arranged along thecross-section of the stirring vessel, at predetermined intervals andparallel to each other, the spacing between said intermediate wiresbeing set larger than the plastic chips and smaller than the particlesof the friction assisting material, the delivery area wires and theintermediate wires differing from each other in direction peripherallyof the stirring vessel.
 3. A frictional charging device as set forth inclaim 1, characterized in that the stirring vessel is inclined such thatthe delivery port side is positioned below the level of the loading portside.
 4. A frictional charging device as set forth in claim 1,characterized by including a delivery area adjuster for adjusting thearea of the opening in the delivery port.
 5. A frictional chargingdevice as set forth in claim 1, characterized by including a stirringmember disposed in the stirring vessel for stirring the plastic chips.6. A frictional charging device that charges crushed chips of aplurality of kinds of plastics by stirring them and feeds them to anelectrostatic separator used for sorting, said frictional chargingdevice being characterized in that an inner sleeve having a number ofopenings extending therethrough is rotatably installed inside an outersleeve, said outer sleeve being provided with a loading port for loadingplastic chips into the outer sleeve, and a delivery port for deliveringthe plastic chips, delivered from the inside of the inner sleeve, to theoutside of the outer sleeve, wherein in order that chips of a particularkind of plastic to be sorted out and plastic chips having a positive ornegative polarity reverse to that of said chips of said particular kindof plastic, in the electrification rank for a plurality of kinds ofplastics forming the chips, may be equal in proportion to each other,particles of either of said plastics are put as a friction assistingmaterial in the inner sleeve, the particles of said friction assistingmaterial being so formed that they are larger than the plastic chips,the openings in said inner sleeve being formed to be larger than theplastic chips and smaller than the particles of the friction assistingmaterial.
 7. A frictional charging device as set forth in claim 6,characterized in that the inner sleeve is rotatable around a horizontalaxis, the loading portion is formed in the upper region of the outersleeve, while the delivery portion is formed in the lower region of theouter sleeve, and said inner sleeve is located at a vertical positionbetween the loading portion and the delivery portion.
 8. A frictionalcharging device as set forth in claim 6, characterized in that the innersleeve is composed of an inner sleeve main body shaped like a sleeve,and end members for closing opposite ends of said inner sleeve mainbody, and said inner sleeve main body and said end members arerespectively formed with a number of openings.